Traditional systems for delivering broadcast media information rely on the use of a physical tuner in a client module (e.g., a television set) that tunes to and receives the media information. In this traditional model, a user can quickly change channels, resulting in the virtual instantaneous transition from one program to another. And as such, the user does not typically perceive a delay in the presentation of a new program upon tuning to a new program. However, this simple manner of operation does not apply to the delivery of digital media information in streaming fashion over a network. In this environment, the client module typically must store a prescribed amount of media information in a buffer before it begins to play the media information to the user. It requires a certain amount of time to fill up this buffer when the user first connects to a stream of media information. Further, digital media information is commonly expressed as a series of key frames (e.g., I frames) and difference frames (e.g., B and P frames). A client module must wait for a key frame before it begins to present the media information. As a result of these factors, there will be a noticeable lag prior to the presentation of programs as the user switches from one channel to the next.
Microsoft Corporation of Redmond, Wash., has developed several strategies that reduce the effects of the above-noted problem in media streaming environments. These strategies are generally referred to as Accelerated Channel Change (ACC) paradigms herein, since they permit the client module to display a new program in an expedited manner when a user “tunes” to the new program (or when the user otherwise commences presentation of the new program). In these strategies, the head-end infrastructure delivers an initial burst which feeds a large quantity of media information to the client module via a communication channel, enabling it to begin presentation of the media information on an expedited basis. After the initial burst, the head-end infrastructure delivers the media information to the client module at a regular data rate (e.g., at or below a specified nominal data rate).
Generally, the ACC strategies make additional demands on the communication channels beyond that required to transmit the media information at its normal steady-state rate. A system can address these demands by allocating extra bandwidth to implement the ACC strategies. However, many environments allocate a limited amount of bandwidth to the communication channels. The application of ACC strategies in these kinds of environments may present various challenges. For example, there is a potential that the ACC strategies can overburden the communication channels, leading to their over-saturation. Such over-saturation of the channels can result in a poor quality of media presentation (e.g., due to the loss of an unacceptable number of media packets). Such over-saturation can also possibly result in the streams being dropped. For example, consider a household that includes various media presentation units that all “feed off” of a single communication channel. The ACC strategies have the potential of overburdening such a communication channel, particularly when multiple users in the household happen to be consuming media information at the same time (and also potentially invoking the ACC behavior at the time).
Other rate-limited environments may allocate a relatively large amount of bandwidth to the channels, thus reducing the potential of over-saturating the channels. It is nevertheless beneficial to adapt the ACC strategies in these environments so as to make efficient use of the allotted communication resources. In any environment, it is also beneficial to find ways to streamline the ACC protocol to make it less costly, less error prone, and more efficient.
For at least the above-identified reasons, there is a need for an improved paradigm for performing accelerated channel change (ACC) in rate-limited environments of all kinds.